Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$57.91	11.520%	$64.5812	$64.58	$64.60	$64.60
Purchase #2	$172.99	11.531%	$192.9375	$192.94	$192.95	$192.90
Purchase #3	$235.56	11.700%	$263.1205	$263.12	$263.10	$263.10
Purchase #4	$152.82	12.247%	$171.5359	$171.54	$171.55	$171.50
Purchase #5	$193.82	3.317%	$200.249	$200.25	$200.25	$200.20
Purchase #6	$196.93	13.502%	$223.5195	$223.52	$223.50	$223.50
Purchase #7	$205.40	10.651%	$227.2772	$227.28	$227.30	$227.30
7 purchase totals =	$1,215.43		$1,343.2208	$1,343.23	$1,343.25	$1,343.10